Learning Objective: Understand the structure, classification, and identification of primary and permanent teeth as well as their clinical relevance in a single, clear conceptual sequence.
Primary and Permanent Dentition
The human dentition consists of two sets of teeth—primary and permanent—arranged into maxillary and mandibular arches that divide into left and right halves along the midline. Teeth sit in alveolar sockets and are anchored by the periodontal ligament.
Primary Dentition:
- 20 teeth (10 per arch).
- Five teeth per quadrant: A–E (2 incisors, 1 canine, 2 molars).
- Erupt: ~6 months onward.
Permanent Dentition:
- 32 teeth (16 per arch).
- Eight teeth per quadrant: 1–8 (2 incisors, 1 canine, 2 premolars, 3 molars).
- Eruption begins ~6 years; completed by ~13 years except 3rd molars (~21 years).
Activity
Tooth Structure
Each tooth has a crown (visible clinical part) and a root (embedded in bone). The anatomic crown is covered with enamel, while the anatomic root is covered with cementum.
Enamel:
Hard, avascular, high mineral content; protects internal tissues; prone to caries and erosion.
Cementum:
Softer, sensitive; exposed to trauma or periodontal disease.
Dentine:
Vital, innervated tissue beneath enamel/cementum; forms most of the tooth.
DEJ:
Junction between dentine and enamel.
CEJ:
Junction between cementum and enamel.
Pulp cavity:
Contains neurovascular structures.
Apex & apical foramen:
Pathway for nerves and blood vessels.
Activity
Identifying Teeth
Teeth are classified as incisors, canines, premolars, and molars, named in the order: dentition – arch – quadrant – tooth type
(e.g., “permanent mandibular right lateral incisor”).
Incisors
Eight in each dentition (maxillary and mandibular). Designed for cutting food. Prone to traumatic injury in children.
Canines
Four in each dentition. It possesses a strong cusp for tearing food. Have long, stable roots. Can remain unerupted in cases of crowding, often located in the palate or buccal sulcus.
Premolars
Present only in permanent dentition (8 total). Usually have two cusps. Often extracted for orthodontic reasons.
Molars
Primary dentition: 8 molars.
Permanent dentition: 12 molars (including wisdom teeth).
Function: grinding and crushing food.
High risk for caries due to deep fissures and broad contact points.
